Free and Open Source Software for Geospatial (FOSS4G) Conference Proceedings Volume 16 Bonn, Germany Article 8 2016 Semantic Markup for Geographic Web Maps in HTML Malte Reißig Leibniz Institute for Regional Geography (IfL), Leipzig, Germany Follow this and additional works at: https://scholarworks.umass.edu/foss4g Part of the Geographic Information Sciences Commons, and the Other Computer Sciences Commons Recommended Citation Reißig, Malte (2016) "Semantic Markup for Geographic Web Maps in HTML," Free and Open Source Software for Geospatial (FOSS4G) Conference Proceedings: Vol. 16 , Article 8. DOI: https://doi.org/10.7275/R52V2D9J Available at: https://scholarworks.umass.edu/foss4g/vol16/iss1/8 This Paper is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Free and Open Source Software for Geospatial (FOSS4G) Conference Proceedings by an authorized editor of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. Semantic Markup for Geographic Web Maps in HTML Malte Reißig Leibniz Institute for Regional Geography (IfL), Leipzig, Germany – [email protected] KEYWORDS: Geographical Web Maps; HTML; Schema.org; Dublin Core; ABSTRACT: In the recent years more and more geographical web maps have been developed and published on the Open Web Platform. Technically this has turned all variants of these maps into documents of the Hypertext Markup Language (HTML) making them appear to us naturally as graph-like and semi-structured data. In this dispute with geographical web maps and HTML we draw on the notion of so called “map mashups”. Requiring an alternative model and definition of what such a map is, our research allows us to build and refine supportive technology which helps us in analyzing and interpreting information map makers code into their visualizations. The spectacles we take on to shine light on the current authoring practices behind many geographical web maps are informed by the perspective of a “critical map reader”. A task-oriented conception of “map critique” helped us to deduce a meaningful user perspective from which we specifically call the semantic web community for support on how to represent various information presented in maps from many authors and sources. With this perspective and questions in mind we investigated the Schema.org vocabulary as an ontology to use for turning elements of geographic web maps into textual statements referencing entities in the “outer world”. To illustrate and to make our investigation of the corresponding web standard documents easily applicable for map makers, to open up the discussion, but also to challenge and develop our first conclusions, we implemented them as a minimal extension to the standard API of the LeafletJS open source web mapping library. 1 Motivation As investigations into the “evolving web mapping technologies” by Roth et al (2014) highlight, more and more geovisualizations are developed and published as HTML Documents. For this report we investigated arbitrary LeafletJS based examples simulating “map mashups” (see Turner, A. J. 2006, Gartner, G. 2009) to think about the semantics of the markup generated, especially those semantics concerned with terminology from the geographic domain. Through Bittner et al we receive our focus on advancing the semantics of map mashups, as the number of geographic web maps published on the world wide web seems to difficult to keep track with. Map mashups on the web, they describe, are essentially “users mixing information with so called base maps through geo-referencing” (after Roth/Ross 2009 and Cramption 2010, see Bittner, C.; Michel, B. 2013, p.112). This report is inspired by the publications of Roth, R. E. (2013) and Schiewe et al which illustrate how a more “wholistic understanding of map usage” (Schiewe, J.; Schweer, M. 201, p. 9) can inform cartographic research. Following a user-centered investigation of semantic markup for geographical web maps, we argue that it is possible to make “critical map reading” an explicit, interactive and possibly even engaging part of the everyday geographic web map experience. Up to my knowledge there is no research reported yet which investigates and refines geographic web maps as what they also have become: documents of HTML. I do so in the hope to equip future map makers and publishers with some knowledge about semantic markup and therewith contribute to a more responsible publishing of geographic web maps, a publishing which not oly considers the map readers perspective but accounts for that through providing advanced accessibility and transparency on information composed in its maps. 2 Introduction to HTML and geographic web maps When we surf geographical web maps on the world wide web we find out that we can understand them as a thing of composite structure, authored, represented and described in documents of the Hypertext Markup Language (HTML). Strikingly, we could not find any description of what a meaningful markup of a geographic web map could be viewed as, thus this investigation. If we understand geographic web maps as composites it FOSS4G 2016 Academic Track Semantic Markup for Geographic Web Maps becomes clearer that a HTML document enclosing such a map aggregates many documents, not just one. Through utilizing web mapping libraries map makers effectively turn geodata of various formats into HTML elements while that is a "domain specific" vocabulary and "mixed markup language". This acknowledges that its a "formal language" used to encode rules for presenting and describing data (see, for example Wikipedia Community 2016). But how does this language reflect our current practices and what are current possibilities to adapt the HTML vocabulary? Advancing our markup through bringing in elements and attributes with meaning anchored in the geographical domain would allow us to make geographical conceptions and data contained in each map explicit and accessible. Having these values accessible would us to build supportive tools and visualizations to match our current web mapping practices. To define the scope of this research and to define what I would call a valuable and improved document structure for a geographical web map is, it must help to give answers about WHO states (or stated) WHEN WHAT about WHOM or WHAT in this map. So, for analyzing maps we rely on questions like: Who contributed to this map? What topics are represented in this map? What areas of the world does the map explicitly deal with? When was this map made? We can easily deduce these questions from course materials on "critiquing maps" by Mattern, S. C. (2016) as well as from the MediaSmarts (2016) guide to "Deconstruct Webpages" for the "7th-10th Grade". With that, it seems logical to state that what is missing to answer these questions are data values accessible in HTML concerning each basic element (Popup/Detail, Marker/Feature or Layer/Geometry) in a map mashup, covering at least an elements Title, Caption, Source, Attribution and Date. In some case these values may already be available in the archive, library or public database providing map makers their information or geodata but yet there does not seem to exist an interface these values could be passed on to. 2.1 Typing of relevant geographic web map elements with Schema.org To express more specific semantics than those defined by the HTML Standard the W3C and others developed HTML Markup Extensions which allow users of HTML to extend the HTML vocabulary into their domain without invalidating the HTML for interpreters. One W3C (2015b) recommendation is Schema.org. According to companies like Google that is well supported by “many major search engines” (2016). The available notations for the latter are Microdata (W3C, 2013), RDFa (W3C, 2015a) and JSON-LD (Sporny, M, Longley, D., Kellogg, G., Lanthaler, M., Lindstrm, N., 2010). To allow basic annotation like I would envision it, the vocabulary must contain terms and definitions for formalizing spatial data values inherent to each geographic web map. Furthermore, essential elements of a geographic web map should be annotatable as (a) distinct elements of information and (b) information representing a certain type of information (like City or Organization) and, one level higher, possibly even a concrete token or instance of such (like Leipzig or Leibniz- Institute for Regional Geography). If these needs could be met I would argue that semantic authoring of geographic web maps has been significantly advanced. The World Geodetic Systems has become without a doubt a useful index to all kinds of information on the web but many map makers might not be aware of the fact that they are not directly exposing their information to it when creating a web map. To express values related to a specific geographic reference system we found that the geo (WGS 84) looks to be integrated with many other linked data vocabularies (http://lov.okfn.org/- dataset/lov/vocabs/geo) but for us of too limited scope. The Schema.org vocabulary allows us to express Geo Coordinates (including elevation) while also allowing for more complex data definitions such as Geo Shape. As this investigation will show, when annotating basic elements of a geographic web map the elements mapped are connected to the WGS 84 reference system but this connection is not accessible when inspecting the HTML of, for example, the LeafletJS example (http://leafletjs.com/examples.html) documents. I therefore took a closer look at the geographic terms provided